Recently the need for improved vaccines for protection against anthrax has become the focus of increased attention. The current vaccine has a considerable number of drawbacks including the requirement for multiple immunizations over an eighteen-month period to obtain levels of immunity commensurate with protection. We have developed novel vaccine delivery systems, which generate rapid, potent and durable antibody responses to protein antigens after a single, subcutaneous administration. The availability of recombinant anthrax protective antigen (rPA) provides an incentive to propose Proof of Concept studies in mice and rabbits with novel formulations of this purified vaccine candidate. The delivery system consists of the thermal-setting block copolymer, PluronicrF127, in combination with selected immunomodulators. We will conduct dose-response studies in mice and rabbits with rPA and measure antibody responses by ELISA and toxin neutralization assay. In addition, responses will be compared to those elicited by rPA adsorbed to aluminum hydroxide. If this Phase I study demonstrates production of toxin neutralizing antibodies and lack of adverse reactions in animals, these data will be used to develop a Phase II study in which these formulations will be evaluated for their ability to elicit protection in rabbits following inhalation challenge with B. anthracis.